UNITED STATES POSTAL SERVICE USPS LOST MY RENT MONEY ORDER Baltimore, Maryland

On 12/8/09 I went to the main post office in Baltimore, MD to get a $700 money order, and an envelope to mail the money order in. I completely filled in the money areas of the "to" and "from" and kept my stub (which is the top of the money order). I sealed it and handed the sealed envelope to the teller. On Friday, 12/11/2009 my landlord called me stating the she had not received the money order to her p.o. box. This confused me because it normally only takes 2-3 business days for her to receive anything that I mail to her. It is now Monday, 12/14/2009 and she still had yet to receive it. I personal went back to the main post office today, with receipts in hand to verify what has happened. I explained to a supervisor and all I could be told was that the holiday mail may have delayed the delivery and/or it could be stuck to another piece of mail, but I was assured that the money order has not been cashed, like that was going to relieve me that $700 is just out on a limb, somewhere and nobody knows. So, to insure my landlord I made a copy of my receipts the mailed that to her. So, can anybody tell me how long does mail take from Baltimore, MD to Germantown, MD? Would the holiday mail normally cause a delay in regular mail? And, why if the receiver has not received the money order and it has been verified that it has not been cashed, why do I need to file a report/grievance with the post office and still wait up to 30-60days for my money to be reimbursed? This is my rent, I don't know about anybody else buy I don't have another $700 just laying around. I'm mad as hell!